"Partner" is very confusing when used by straights. I get why it's used (more serious/adult than boyfriend/girlfriend), but I always think the person is telling me he/she is gay. The straight friend use of "girlfriend" is similarly confusing.

Yeah, I get confused by the "girlfriend" thing too.

but I always think the person is telling me he/she is gay.

I do wonder if whoever reads it thinks I'm gay (though The Boy's name is unequivocally a man's name), or thinks that he's my business partner or something.

I think after seven years, it's common-law marriage or something?

Not quite -- in the US version of the thing, there are a few states that allow marriage by declaring yourselves to be married (as opposed to getting a license from the gummint); this can include either doing a thing in front of witnesses or living/presenting yourselves as if married. This all goes back to English law before the marriage law reforms of the 1750s*, and so only exists in states that adopted their local laws way back then: definitely Pennsylvania, maybe New Hampshire and a few other legal oddballs? In none of those places is there an automatic "you're hitched if you live together for xxyy years"** without intention to marry, and in the places where it does exist, the rules vary widely.

* also crucially important in racy Regency-era abduction plots! Or any time you see people running off to Gretna Green!

** but boy did we scare ourselves in high school with the idea that you might end up ACCIDENTALLY OMG MARRIED

(IANAL, just freaky-researchy and easily amused.)

When my mother was not yet married to her now-husband, I was stumped as what to call him. He was in his 60s and rather portly and serious-looking - not a boyfriend. He had a partner - a partner in his dentistry office. I sometimes went with "gentleman friend."

Like when you're talking about somebody you go to the mall with and say "Nice earrings...my girlfriend Cheryl has them in black." I used to do this more when I had fewer gay friends. Also "hey, girlfriend!" seems to have met the same fate as "posse"

When my mother was not yet married to her now-husband, I was stumped as what to call him. He was in his 60s and rather portly and serious-looking - not a boyfriend

When Lewis and I lived together, before we were married, his mother used to refer to me as his "special friend."

Which caused us no end of amusement.

After our first 10 years together, our parents started lobbying for better titles for us. Once when my FiL asked me "What should I introduce you as? This is Jason's..." I said "Reason for living." He used that for quite a while.

Do Americans not use 'partner' very widely (for straight relationships), then? I hear it as much for long-term straight relationships as for gay ones. It's handy to be able to say 'my partner' and not necessarily have to come out in the process.

It's an especially useful term among people who would sound silly announcing that they had a 'girlfriend'. Such as my 53-year-old father. (He tried 'lady friend' out once, but it made us all fall about laughing, so he stopped.)

Also "hey, girlfriend!" seems to have met the same fate as "posse"

Passe?